A DFT and crystallographic reinvestigation of the [L_2RuC _2B_7H_9] and [L_3RuC_2B _7H_9] 'hypercloso' and closo systems

摘要

A reinvestigation of the [LRuC_2B_7H_9] 'hypercloso' 10-vertex cluster compounds, where L = PPh3, PEt 3, which were first reported some 30 years ago, has been carried out. At that time no single-crystal X-ray diffraction structural analysis was obtained for the compounds and their description as featuring a 'hypercloso' cluster constitution, where the descriptor hypercloso is defined as being a closed polyhedral structure possessing n skeletal bonding electron pairs, where n is the number of vertices, was largely based on a combination of chemical and NMR spectroscopic evidence, together with the application of Polyhedral Skeletal Electron Pair Theory as it was then understood. Reported here is a single-crystal Xray diffraction study of the PPh_3 ligated ruthenacarborane allied with density functional calculations (DFT). The cluster structure is shown to be of isocloso geometry, albeit with considerable distortion towards isonido. Addition of excess PMe3 leads to the formation of an [(PMe _3)_3RuC_2B_7H_9] species of conventional 10-vertex closo geometry but it undergoes a cluster rearrangement, resulting in a different isomer to that originally proposed. 2011 Elsevier Ltd.